As is well known in the art, vibratory processing equipment has been developed to satisfy a wide range of diverse applications. It is oftentimes the case that a system for handling any of a variety of different materials will include as an integral component a vibratory conveyor. Generally, vibratory conveyors may be used for transporting materials to and through a processing section to a post-processing location. In one particular application, a vibratory conveyor may find advantageous use in a foundry for conveying metal castings or the like from one point to another after they have been formed. There is another very important need to be able to remove sand molds and sand cores and to thereafter reclaim and recirculate the foundry sand which is typically bonded by a resin to form the sand molds and to make the sand cores used in the molds to create interior voids during conventional production of metal castings. After metal castings have been formed, the sand molds and sand cores must be removed, following which the sand must be reclaimed which has typically been accomplished by using a machine called a shake-out.
In this connection, the shake-out is typically of a vibratory nature and operates such that the moisture and clay bonded type sand is simply shaken loose from the metal castings. Optionally, the sand molds and sand cores using resin bonded type sand may be subjected to hot air for the purpose of causing the resin binder in the sand to break down so that the sand will fall away from the metal castings and core passages. In either case, the sand will typically be collected in the bottom of a chamber for further heat or chemical processing to remove any remaining resin to thereby reclaim the sand which is stored for later reuse.
As shown by Nakanishi, U.S. Pat. No. 4,411,709, it has been known that resin bonded sand molds and sand cores can be removed, and the sand simultaneously reconditioned for re-use, by heating the resin bonded molding sand and core sand at a sufficient temperature to be able to pyrolyze the resin binders in the sand. As explained in Crafton, U.S. Pat. No. 5,354,038, and later in Bonnemasou et al., U.S. Pat. No. 5,423,370, it may be advantageous for this heating to be accomplished by utilizing a fluidized bed of sand particles. In particular, Bonnemasou et al. U.S. Pat. No. 5,423,370 point outs that fluidized beds are useful for removing the sand cores from cast aluminum parts, but it also cautions that, when hot, these cast aluminum parts are such that they cannot tolerate "even modest handling."
Moreover, while it is known to use heat to reclaim the sand by pyrolyzing the resin bonding material or binder, this poses a seemingly unresolvable dilemma; namely, how to apply sufficient heat for efficient pyrolyzing of the bonding material in a manner achieving significant energy conservation. There is also a related problem in that metal castings must typically be heat treated at a specific temperature which must be controlled within close tolerance in order to avoid damage to the castings while at the same time providing a highly efficient and effective heat treatment environment. While the temperature for heat treating the metal castings may be sufficient for decoring purposes, i.e., for removing the cores that are formed of sand and resin bonding material or binder from the castings to reclaim the sand, that same temperature may not be sufficient to reclaim the sand by pyrolyzing the resin bonding material or binder.
Particularly for aluminum castings, the important competing requirements for (1) efficiently and effectively heat treating the castings in an environment where the temperature is controlled within close tolerance, (2) decoring the castings by removing the core sand therefrom, and (3) reclaiming the core sand for reuse in a manner fully ensuring that the resin bonding material or binder is completely pyrolyzed, may well be best achieved in more than a single stage.
The present invention is directed to overcoming one or more of the foregoing problems while achieving one or more of the resulting objects by providing a unique vibratory heat treating, decoring, and sand reclamation system.